Fluid hydroforming process with inverse temperature gradient



Jan- 15, 1957 R. J. FRITZ ETAL 777,803

ELUID HTDRoEoR/IINGy RRocEss WITH lNvERsE TEMPERATURE GRADIENT FiledDec. 2e, 1951 bert Fritz Ed AfZL'doLaz', fQVef'DOr d ard'l .Od olsen.

s Otmar-meg temperatures and pressures in the presence hydroformingcatalyst particles in IWA FLUID HYDROFRMENG PRCESS WlTH INVERSETEMPERATURE GRADIEN' Robert J. Fritz, Lloyd A. Nicolai, and Edward S.

Nicholson, Baton Rouge, La., assignors to Esso Ptesearch and EngineeringCompany, a corporation of Delaware Application December 26, 1951, SerialNo. 263,443 3 Claims. (Cl. 19d-Sil) arent Hydroforming is a well knownand widely used process Y for treating hydrocarbon fractions boilingwithin the motor fuel or naphtha range to upgrade the same or increasethe aromaticity and improve the anti-knock characteristics of saidhydrocarbon fractions. By hydroforming is ordinarily meant an operationconducted at elevated of solid catalyst particles and hydrogen wherebythe hydrocarbon fraction is increased in aromaticity and in whichoperation there is no net consumption of hydrogen. Hydroformingoperations are ordinarily carried out in the presence of hydrogen or ahydrogen-rich recycle Vgas at temperaturesof 750- l150 F. in thepressure range of about 50-1000 lbs. per sq. inch and in contact withsuch catalysts as molybdenum oxide, chromium oxide or, in general,oxides or sulides of metals of groups lV, V, Vl, VII and VIII of theperiodic system of elements, alone, or generally supported on a base orspacing agent such as alumina gel, precipitated alumina or zincaluminate spinel. A good hydroforming catalyst is one containing aboutl0 wt. percent molybdenum oxide upon an aluminum oxide base prepared byheat treating a hydrated aluminum'oxide or upon zinc aluminate spinel.

It has been proposed in application Serial No. 188,236, :tiled October3, 1950, now U. S. Patent No. 2,689,823, to effect the hydroforming ofnaphtha fractions in a iiuidized solids reactor system in which naphthavapors are passed continuously through a dense fluidized bed of areaction zone, spent catalyst particles are withdrawn from the dense bedin the reaction zone and passed to a separate regeneration zone whereinactivating carbonaceous deposits are removed by combustion whereuponthe regenerated catalyst particles are returned to the main reactorvessel or hydroforming reaction zone. Fluid hydrofonning as thusconducted as several fundamental advantages over fixed bed hydroformingVsuch as (l) the operations are continuous, (2) the vessels and equipmentcan be designed for single rather than dual functions, (3) the reactortemperature is substantially constant throughout the bed, and (4) theregeneration or reconditioning ofthe catalyst may be readily controlled.Y

A particular advantage of the foregoing fluid solids operation has beenthe fact that the freshly regenerated catalyst can be utilized to carrypart of the heat required for the hydroforming reaction from theregeneration zone into the reaction zone. lt has been proposed in thisconnection to discharge hot, regenerated catalyst particles from theregenerator Vstandpipe into a stream of hot, hydrogen-rich recycle gasin a transfer line whereby the catalyst particles are subjected to areconditioning treatment involving at least a partial reduction ofhigher incoming gas over ,the entire catalytic metal oxides formedduring regeneration to a lower or more catalytically active form ofcatalytic metal oxide during its passage through the transfer line intothe reaction zone. In view of the high temperature of the regeneratedcatalyst (M50-i300" F.) and the exothermic character of the 'reactionbetween the hot, freshly regenerated catalyst and the hydrogen it isnecessary to make the transfer line small in diameter and veryrshortinorder to keep the time of contact of the catalyst andhydrogencontaining gas suiciently short to avoid overtreatment and/orthermal degradation of the catalyst.

It is the object of this invention to provide a novel method forhandling freshly regenerated catalyst `whereby it may be contacted withhydrogen-containing gas at temperatures well below regeneratortemperature'.`

It is also the object of this invention to efect contact i of freshlyregenerated catalyst with hydrogen-containing gas at relatively lowtemperatures and under conditions which prevent appreciable contact ofpretreatment reaction vapors with the main reaction bed.V

It is a further object of this invention to provide a novel method forhandling freshly regenerated hydroforming catalyst whereby it may becontacted with hydrogen-containing gas at temperatures well belowregenerator temperature while establishing an inverse temperaturegradient in the reactor vessel.

These and other objects will appear more clearly from the detailedspecification and claims which follow.

lt has now been found that freshly regenerated hydroforrning catalystcan be advantageously treated with hydrogen-containing gas if it istransferred to the upper bed of a duo-bed reactor that is operated witha high rate of entrainment from the lower to the upper bed. in this waythe regenerated catalyst is mixed with a large amount of reactorcatalyst thereby reducing its temperature sufficiently low to simplifythe problemcf pretreatment of the catalyst while still effectivelyVtransferring heat from the regenerator to the reactor side. Moreoverthe contact of the hydrogen-containing gas or reaction mixture is undersuch conditions that water vapor formed inthe treatment of theregenerated catalyst with hydrogen-containing gas is rapidly swept awayfrom the dense catalyst bed thereby minimizing the deleterious effectsof the Water vapor upon catalyst activity and selectivity. v In additionthis operation permits the maintenance of a higher average temperaturelevel in the upper bed of the reactor thereby achieving an inversetemperature gradient or higher average temperature for the finalreaction stage in a twoor multi-stage operation, The latter isespecially advantageous sincev it results inutherapplication of the mostdrastic reaction conditions to the reaction mixture Vafter the morereadily hydroformed constituents have' converted. v

Reference is made to the accompanying drawing illustrating a schematicow plan in accordance with the present invention.

In the drawing 10 is a reactor vessel provided with an f to introducethefeed stock separately from the hydrogenline 12. A perforated plate richgas as through feed inlet or distribution grid 13 is arranged in thelowerpart of the reactor vessel to insure cross-section of the reactorvessel. At least one horizontal plate 14 is providedin the upper partand the plate s provided with a downcomer Y15 which maintains at least aminimum bed ofY catalyst above the plate 14 and serves to conduct theoverow of iuidized catalyst from above plate 14 into Vthe been y uniformdistribution of the separator 18 through which the cyclone Vseparator 18near the bottom of regenerator dense bed 16 through perforated plate 14into the dense,

uidized turbulent bed 17 above plate `14 it is necessary to maintain asmall outage or free space between the level Land plate 14. Ordinarilyunder the normal reaction conditions of about 200 lbs. per sq. inch andsuperficial vapor velocities through the reactor of about 0.2 to V1.0

ft. per second the outage should be vless than about 2 feet. As vthepressure and/or the superficial velocity of the vapors are increased theoutage may be increased. The dense fluidized bed 17 upon plate 14 alsohas a definite level L'. 'Sufficient outage or free space should beprovided above level L' or between level L and the inlet to the cycloneseparator to prevent overloading of the cyclone the reaction productsare withdrawn from the reactor. Entrained catalyst separated from theproduct gases in cyclone separator 1S is returned to dense bed 17through the dip leg attached to the bottom of said cyclone separator.The reaction products are taken overhead through product outlet line 19and are passed to suitable fractionating, stabilizing and/or storageequipment. Y

A stream of catalyst is withdrawn continuously from the reactor throughcatalyst mthdrawal line 20 which discharges the spent catalyst intostripper 21 wherein the spent catalyst particles are stripped ofentrained or adsorbed hydrocarbons and hydrogen by means of a strippinggas such as steam, nitrogen or the like introduced at 22. Shipping gasand stripped products are taken overhead from stripper 21 landdischarged into `the dilute phase at the top of the reactor vessel forpassagethrough in order to recover any catalyst entrained in thestripping gas or if it is desired to have the stripping gases by-passthe reactor completely, a direct connection may be made from thestripper Vdirectlv into the products outlet line 19. Y Stripped spentcatalyst is discharged from the base of the stripper into U-bendtransfer line 23 into spent catalyst riser line 24. Air, preferably aportion only of that required for regeneration, is supplied at 25 nearthe bottom of riser 24 in order to reduce the density of the catalyststream in the upflow leg to the point where the catalyst will flowupwardly into the base of regenerator 25. t A perforated plate ordistributor grid 26 is arranged 25 in order to insure uniformdistribution of the .incoming catalyst and regeneraltion gas over theentire cross section of the regenerator.

The velocity of the regeneration gases is so controlled as to form adense, fluidized, turbulent bed 27 in therregenerator and having adefinite level L" entraiued in the regeneration gases. The regenerationgases are taken overhead through a cyclone separator Y 29 for separatingcatalyst particles which are returnedA tothe dense bed 27 through thedip pipe attached to the oxidative reactions that occur in theregenerator generate more heat than can normally be transferred to thereactor by the circulating catalyst at low catalyst to yoil ratioswithout exceeding safe temperature limits, it is ordinarily vnecessaryto provide cooling coils in the regenerator to prevent the regeneratortemperature from exceedingA al Vsafe upper limit. A very desirablearrangement is to provide a primary cooling oil entirely belowA thedense superposed by av dilute phase 28 Lcomprising small amountsv ofcatalyst =zinc alumiuate spinel or the like.

bed .level L" and a secondary coil partly belowk and partly above thedense bed level L" to permit adjustment ofthe heat exchange capacity bysimply varying the dense bed level L in the regenerator.

Hot, freshly regenerated catalyst is withdrawn directly from the densebed 27 through regenerated catalyst withdrawal line 31. Stripping gassuch as air, nitrogen, flue gas or the like is introduced at 32 nearthelower part of line 31 in ordertoV strip the regenerated catalyst ofentrained regeneration gases. The fiow of regenerated cataf lyst throughline 31 is controlled by slide valve 33 and the catalyst is thendischarged into the upperrdense bed 17 in the reactor. By maintaining ahigh rate of entrainment from bed 16 as by maintaining a small outageVor free space between vthe top L'of dense bed 16 and the plate 14,sufficient reactor catalyst may be carried from dense bed 16 into bed 17to effectively control or reduce the temperature of the hot freshlyregenerated catalyst from regenerator temperatures of about 1050-1300 F.to below about 950 F. for a reactor temperature of 900 F. The lattertemperature is sufficiently low that the treatment of the regeneratedcatalyst with hydrogen proceeds only so far as to result in an activevalence form of the molybdenum, and there `is no need for terminatingthe treatment as quickly as possible inasmuch as no overreduction canoccur at these temperature levels. Moreover a temperature about 50 F.above that on the main reactor is advantageous in effecting a conversionof some of the more refractory constituents of the feed stock.

rl`he feed or charging stock to the hydroforming reactor may be a virginnaphtha, a cracked naphtha, a Fischer-Tropsch naphtha yor the like. Thefeed stock is preheated alone or in admixturewith recycle gas toreaction temperature or to the kmaximum temperature possible whileavoiding thermal degradation of the feed stock. Ordinarily preheatingofthe feed stock is carried out to temperatures of about SOO-1050" F.,preferably about 1000 F. The naphtha preheat should be as high aspossible while avoiding thermal degradation thereof as by limiting thetime of residence in the furnace and the transfer or feed inlet lines.Thev preheated feed stock may be supplied to the reaction vessel inadmixture with hydrogen-rich recycle f gas orr it may beintroducedseparately as shown. The recycle gas, which contains from about 50 to 80vol. percent hydrogen, is preheated to temperatures of about 1050-1300"F., preferably about 1200 F., prior to the introduction thereof intoinlet line 11. The recycle, gas should be circulated through the reactorat a rate of from about 1000 to 8000 cu. ft. perbarrel of naphtha feed.`The amount of recycle gas should be the minimumfthat will suffice tointroduce the necessary heat of reaction and still maintain carbonformation at a'low level. 1

The reactor system is charged with a massk of finely dividedhydroforming catalyst particles.v Suitable catalysts include group VImetal oxides, such as molybdenum oxide, chromium oxide, ortungsten'oxide, or mixtures thereof upon a carrier such as activatedalumina, Preferred catalysts contain about 5 to 15 wt. percentmolybdenum oxide or from about l0 to 40 wt. percent chromium oxide upona suitable carrier. lizers and promoters such assilica, calcium oxide,ceria or potassia can be included in the catalyst. The catalystparticles are, for the most part, between and 400 mesh in size or about0-200 microns in diameter with a major proportion between 2O and 80microns.

The hydroforming reactor vessel should be operated at temperaturesbetween about 850 and 950 F., preferably at about S75-900 F. in thefirst reaction zone or lower bed 16 and at about 900-950 F. in the finalreaction zone or upper bed 17. The pressure in the reactor system shouldbe between 50 and v500 lbs. per sq. inch, preferably about 200 lbs.per'sq. inch. Temperatures above 900 F. result in increased carbonformation and lower selectivity to gasoline fractions while at Ifdesired, minor amounts of stabif temperatures. below about SQQ"operating. severity is low and would` therefore require 'an excessivelylarge reaction vessel. Ordinar-ily, lowering reactor pressure below 200lbs.- per s q.. inch results in increased carbon formation whichvbecomes excessive in most cases below about 75 lbs.V per sq.Y inch..Above 200 lbs., however, Qtitalyst selectivity to. light products (Cmand lighter) increases rapidly. The regeuerator is operated atessentially the same pressure as the reactor and at temperatures ofabout 1050-l300 F., preferably yabout 1200 F. The residence time of thecatalyst in the reactor is of the order of from about 3 to 4 hours,while the residence time of the catalyst in the regenerator is of theorder of about 3 to 15 minutes.

The weight ratio of catalyst to oil introduced into the reactor shouldbe about 0.5 to 1.5. It is preferred to operate at catalyst to oilratios of about 1, since ratios above about 1 to 1.5 result in excessivecarbon formation. Somewhat higher weight ratios can be used at higherpressures.

Space velocity or the weight of feed in pounds charged per hour perpound of catalyst in the reactor depends upon the age or activity levelof the catalyst, the character of the feed stock and the desired octanenumber of the product. Space Velocity for a molybdenum oxide or aluminumgel catalyst may vary, from about 1.5 wt./hr./wt. to about 0.15wt./hr./wt.

For a typical case, operating conditions and temperatures are givenbelow for operation on 'a light virgin naphtha of 57 API gravity.

Feed rate 20,000 B./D. C/O ratio 1.0 Recycle rate 5,000 C. F./B Severity0.25 wt./hr./wt. Regenerator temperature 1200 F. Pretreat and cleanupsection of re- 925 F.

actor. Main body of reactor 875 F.

Catalyst circulation rate Catalyst circulation to pretreat section forcooling.

Total gas leaving reactor 1,000,000 C. F. H.

' (at 875 F. and

200 p. s. i. g.).

1.42 lbs/C. F.

218,000 lbs/hr. 1,420,000 lbs./ hr.

Required entrainment to pretreat section to cool incoming regeneratorcatalyst.

Entrainments at 200 p. s. i. g. at reactor conditions of 1.4 lbs/C. F.can be obtained at about 1 ft. outage. With a 40 lbs/cu. ft. catalystdensity, the 1 ft. outage can be obtained by designing the grid belowthe pretreat section for approximately 8 inches of H2O pressure drop. Itwill be noted that for the base conditions, a 4 hour reactor holdingtime is obtained. It is desired to have the hold-up in the pretreatsection Ve to 1A of the total reactor hold-up. Since the initial phasesof the reduction take place quickly, only a very small portion of thecatalyst in the pretreating section is unreduced at any time.

The foregoing description contains a limited number of embodiments ofthe present invention. It will be understood, however, that numerousvariations are possible without departing from the scope of thefollowing claims.

What is claimed is:

l. In a process for hydroforming hydrocarbons in contact with finelydivided hydroforming catalyst particles consisting essentially of aGroup VI metal oxide dispersed upon a carrier in accordance with theuidized solids technique at temperatures of from about 850950 F.,pressures of from about 5 0 to 500 pounds per square inch, and atcatalyst to oil weight ratios of from about 0.5-1 to about 1.5-1 theimprovement which comprises mainfor example, y

two dense, luidized beds of hydroforming catalyst in vertically spacedrelation to each other in a reaction zone, maintaining theupper denseuidized bed at a substantially higher temperature than the lower denseuidized bed, passing hydrocarbon feed vapors preheated to about 8001050F. and hydrogen-rich gas preheated to 1050-1300 F. upwardly through saidbeds in series, the amount of hydrogen-rich gas being about 1,000 toabout 8,000 cubic feet per barrel of liquid feed continuouslywithdrawing a stream of spent catalyst particles from the lower densebed in the reaction zone, regenerating the withdrawn spent catalystparticles by burning carbonaceous deposits therefrom at temperatures ofabout 10501300 F., recycling hot regenerated catalyst particles to theupper dense uidized bed in the reaction zone, maintaining a high rate ofentrainment of catalyst particles from the lower dense bed `to the upperdense bed in the reaction zone in order to control the temperature ofthe freshly regenerated catalyst in contact with the hydrogen-containingreaction mixture in said upper dense bed.

2. In a process for hydroforming hydrocarbons in contact with finelydivided hydroforming catalyst particles consisting essentially of aGroup VI metal oxide dispersed upon a carrier in accordance with theiluidized solids technique at temperatures of from about 850950 F.,pressures of from about 50 to 500 pounds per square inch, and atcatalyst to oil weight ratios of from about 0.5-1 to about 1.5-l theimprovement which lcomprises maintaining Atwo dense, lluidized beds ofhydroforming catalyst in vertically spaced relation to each other in areaction zone, maintaining the lower dense bed at a temperature ofS75-900 F. and the upper dense bed at 90o-950 F., passing hydrocarbonfeed vapors preheated to about G-1050 F. and hydrogen-rich gas preheatedto 1050-1300 F. upwardly through said beds in series, the amount ofhydrogen-rich gas being about 1,000 to about 8,000 cubic feet per barrelof liquid feed continuously withdrawing a stream of spent catalystparticles from the lower dense bed in the reaction zone, regeneratingthe Withdrawn spent catalyst particles by burning carbonaceous depositstherefrom at temperatures of about 1050-l300 F., recycling hotregenerated catalyst particles to the upper dense fluidized bed in thereaction zone, maintaining a high rate of entrainment of catalystparticles from the lower dense bed to the upper dense bed in thereaction zone in order to control the temperature of the freshlyregenerated catalyst in contact with the hydrogen-containing reactionmixture in said upper dense bed.

3. In a process for hydroforming hydrocarbons in contact with finelydivided hydroforming catalyst particles consisting essentially of aGroup VI metal oxide dispersed upon a carrier in accordance with theuidized solids technique at temperatures of from about 850-950 F.,pressures of from about 50 to 500 pounds per square inch, and atcatalyst to oil weight ratios of from about 0.5-1 to about 1.5-1 theimprovement with comprises maintaining two dense, uidized beds ofhydroforming catalyst in vertically spaced relation yto each other in areaction zone, maintaining the lower dense bed at a temperature ofS75-900 F. and the upper dense bed at 900-950" F., passing hydrocarbonfeed vapors preheated to about 800-1050 F. and hydrogen-rich gaspreheated to 1050l300 F. upwardly through said beds in series, theamount of hydrogen-rich gas being about 1,000 to about 8,000 cubic feetper barrel of liquid feed continuously withdrawing a stream of spentcatalyst particles from the lower dense bed in the reaction zone,regenerating the withdrawn spent catalyst particles by burningcarbonaceous deposits therefrom at temperatures of about 1050-l300 F.,recycling hot regenerated catalyst particles to the upper denseiiuidized bed in the reaction zone,

I Y References Cited in the tile of this patent UNITED STATES PATENTSMeinert et al.` Nov. 12, 1946 Hall et al May 24, 1949 Barr Oct. 4, 1949Gerhold Feb. 12, 1952

1. IN A PROCESS FOR HYDROFORMING HYDROCARBONS IN CONTACT WITH FINELYDIVIDED HYDROFORMING CATALYST PARTICLES CONSISTING ESSENTIALLY OF AGROUP VIMETAL OXIDE DISPERSED UPON A CARRIER IN ACCORDANCE WITH THEFLUIDIZED SOLIDS TECHNIQUE AT TEMPERATURES OF FROM ABOUT 850*-950*F.,PRESSURES OF FROM ABOUT 50 TO 500 POUNDS PER SQRARE INCH, AND ATCATALYST TO OIL WEIGHT RATIONS OF FROM ABOUT 0.5-1 TO ABOUT 1.5-1 THEIMPROVEMENT WHICH COMPRISES MAINTAINING TWO DENSE, FLUIDIZED BEDS OFHYDROFORMING CATALYST IN VERTICALLY SPACED RELATION TO EACH OTHER INA AREACTION ZONE MAINTAINING THE UPPER DENSE FLUIDIZED BED AT ASUBSTANTIALLY HIGHER TEMPERATURE THAN THE LOER DENSE FLUIDIZED BED,PASSING HYDROCARBON FEED VAPORS PREHEATED TO ABOUT 800-1050*F. ANDHYDROGEN-RICH GAS PREHEATED TO 1050-1300*F. UPWARDLY THROUGH SAID BEDSIN SERIES, THE AMOUNT OF HYDROGEN-RICH GAS BEING ABOUT 1,000 TO ABOUT8,000 CUBIC FEET PER BARREL OF LIQUID FEED CONTINUOUSLY WITHDRAWING ASTREAM OF SPENT CATALYST PARTICLES FROM THE LOWER DENSE BED IN THEREACTION ZONE, REGENERATING THE WITHDRAWN SPENT CATALYST PARTICLES BYBURNING CARBONACEOUS DEPOSITS THEREFROM HOT REGENERATED CATALYSTPAR1050-1300*F., RECYCLING HOT REGENERATED CATALYST PARTICLES TO THEUPPER DENSE FLUIDIZED BED IN THE REACTION ZONE MAINTAINING A HIGH RATEOF ENTAINMENT OF CATALYST PARTICLES FROM THE LOWER DENSE BED TO THEUPPER DENSE BED IN THE REACTIONZONE IN ORDER TO CONTROL THE TEMPERATUREOR THE FRESHLY REGENERATED CATALYST IN CONTACT WITH THEHYDROGEN-CONTAINING REACTION MIXTURE IN SAID UPPER DENSE BED.